the deposited Au
layers and formed gold oxide films was measured by ellipsometry (M-2000UI,
J.A. Woollam Co., United States) at an angle of 75°. The surface
roughness of the deposited Au layers was measured by atomic-force
microscopy (AFM, Dimension Icon, Bruker Corp., USA) with a contact
mode in air. HR-SEM images were captured with a high-resolution scanning
electron microscope (FEI Sirion, USA) at a 5 kV acceleration voltage
and a spot size of 3. The contact angles of a DI water drop on Au
surfaces were measured by using an interfacial tension meter (OCA
15 Pro, Dataphysics Instruments GmbH, Germany) at ambient temperature.
TEM specimens were prepared by using a focused ion beam (FIB) system
(FEI Nova 600 NanoLab FIB, USA). The TEM analysis was performed with
a Philips CM300ST-FEG TEM system (The Netherlands) at a 300 kV acceleration
voltage.